Susceptibility of bacterial isolates to vancomycin and ceftazidime from patients with endophthalmitis: Is there a need to change the empirical therapy in suspected bacterial endophthalmitis?

To review the susceptibility of bacterial isolates to ceftazidime and vancomycin isolated from patients with endophthalmitis. Microbiology records of patients with endophthalmitis between June 2010 and May 2013 were reviewed. Vitreous and AC fluids obtained from patients with endophthalmitis were subjected to direct microscopy examination and culture. Antibiotic susceptibility of the isolates was performed by Kirby Bauer disk diffusion method. Resistant to ceftazidime in Gram negative bacteria (GNB) by disk diffusion method is confirmed by minimum inhibitory concentration using E test. Culture was positive for bacteria/Fungi in 224/356 patients (62.9 %). Out of 224 patients, 191 (85.2 %) patients showed bacterial growth and 33 (14.0 %) showed fungal growth. Mixed bacterial infection was seen in five patients. Among the GNB, 23/123 (18 %) of the isolates were resistant to ceftazidime, and all the Gram positive bacteria 73/73 (100 %) were susceptible to vancomycin. Sixteen of 123 (13 %) GNB were resistant to amikacin. Although there is an increase in resistance to ceftazidime compared to amikacin in GNB, amikacin intravitreal injection is associated with macular toxicity and no single antibiotic has full coverage for all GNB. Combination of vancomycin and ceftazidime empiric therapy can be continued in patients with suspected endophthalmitis and treatment is modified based on clinical response and susceptibility results.